/Engine/Source/Runtime/Engine/Classes/Engine/GameViewportClient.h
Create the game viewport
virtual [FSceneViewport](API\Runtime\Engine\Slate\FSceneViewport) * CreateGameViewport ( [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SViewport](API\Runtime\Slate\Widgets\SViewport) > InViewportWidget )